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PYtte's avatar
PYtte
Icon for Occasional Contributor rankOccasional Contributor
5 years ago
Solved

MAX10 Internal OSC. Only 55 or 116 Mhz? Nothing between?

I want to use the internal clock and have been successful at using the 116 MHz setting. But when I looked at the the specification it look like you can choose freely between 55 to 116 MHz. "55~116"...
  • ak6dn's avatar
    ak6dn
    5 years ago

    Your last observation is correct. The internal oscillators on these parts are not capable of high accuracy and have a very wide range that they may operate at. Thus you could see the internal oscillator vary from 55MHz to 116MHz and all you can count on is the frequency you will see on a particular part is somewhere in that range. It will also vary over operating temperature and voltage range. Part to part variance will also occur, of course.

    So if you need a precise frequency for operation you MUST use an external reference such as a crystal oscillator based device or a known accurate frequency source.

PYtte's avatar
PYtte
Icon for Occasional Contributor rankOccasional Contributor
5 years ago

That is a solution when you know the frequency but from what I gather you implement the Internal Oscillator and get a frequency within the range of 55 to 115 MHz. There is no way for me to set a specific frequency. If I have a protocol that require precise timing I have to know the clock speed. I can´t have one board where the FPGA is running at 55 MHz and one where it is running at 116 MHz.

I will just implement a external clock on our PCB so I can make sure I have a specific frequency.

  • ak6dn's avatar
    ak6dn
    Icon for Regular Contributor rankRegular Contributor
    5 years ago

    Your last observation is correct. The internal oscillators on these parts are not capable of high accuracy and have a very wide range that they may operate at. Thus you could see the internal oscillator vary from 55MHz to 116MHz and all you can count on is the frequency you will see on a particular part is somewhere in that range. It will also vary over operating temperature and voltage range. Part to part variance will also occur, of course.

    So if you need a precise frequency for operation you MUST use an external reference such as a crystal oscillator based device or a known accurate frequency source.

    • EngWei_O_Intel's avatar
      EngWei_O_Intel
      Icon for Frequent Contributor rankFrequent Contributor
      5 years ago

      Hi Peter

      There are some variations in the internal oscillator frequency because of the process, voltage, and temperature (PVT) conditions. We need external clock source for high accuracy clock.

      Thanks.

      Eng Wei

      • PYtte's avatar
        PYtte
        Icon for Occasional Contributor rankOccasional Contributor
        5 years ago

        Thanks for confirming this. I feel this could have been clearer in the documentation.

        Thanks

        Peter